This invention generally relates to rotors having permanent magnets, and more particularly to rotors of this type which also employ an epoxy resin to fill various internal voids and interstices.
Permanent magnet rotors are frequently used in electric generators to produce an electric current without the need for brushes or other rotating electrical connectors. These generators, for example, are often employed with transport refrigeration machines to deliver an electric current suitable for operating fan or blower motors of the refrigeration machine.
Generally, a permanent magnet rotor includes a housing, a plurality of permanent magnets, an inner ring, and an outer ring. The housing conventionally comprises a pair of substantially identical, circular plates. These plates are parallel, spaced apart, and have aligned central openings defining a shaft opening. The permanent magnets are placed or sandwiched between the housing plates; and the magnets are annularly spaced around the shaft opening, radially between and spaced from both the shaft opening and the outside circumference of the housing plates. The inner and outer rings of the rotor are secured within the housing, between the housing plates; and these rings are respectively located radially inside and outside the permanent magnets, holding the magnets against radial movement.
Typically, the permanent magnets, the inner ring, and the outer ring do not completely fill the space between the plates of the housing, leaving several voids or pockets therein. For many years, these internal spaces were filled with aluminum. Several years ago, I made a major improvement upon the then conventional design of rotors of the general type described above by, among other things, providing a method where the internal cavities and voids of the rotors may be filled with an inexpensive epoxy resin. This improvement is described in detail in my United States patent 4,126,933. While this improvement substantially reduced the cost of the rotors, there was some accompanying reduction in the capacity of the rotors, and over the past several years I have studied these improved rotors to see if their capacity could be increased.